1. Field of the Invention
The present invention relates to an optical material organic compound as well as an optical material and an optical element by using the optical element compound. In particular, the present invention relates to a (meth)acrylate compound having peculiar optical characteristics as well as an optical material and an optical element by using the (meth)acrylate compound.
2. Description of the Related Art
In general, the refractive indices of optical materials composed of glass materials, organic resins, or the like increase gradually with decreasing wavelengths. Examples of indicators representing the chromatic dispersion property of the refractive index include an Abbe number (νd) and a secondary dispersion characteristic (θg,F). The Abbe number and the value of θg,F are values peculiar to individual optical materials and fall within certain ranges in many cases. FIG. 1 is a diagram showing the relationship between the secondary dispersion characteristic (θg,F) and the Abbe number of organic materials (glass materials and organic resins) in the related art.
In this regard, the Abbe number (νd) and the secondary dispersion characteristic (θg,F) are represented by the following formulae.Abbe number(νd)=(nd−1)/(nF−nc)secondary dispersion characteristic(θg,F)=(ng−nF)/(nF−nc)(nd represents a refractive index at a wavelength of 587.6 nm, nF represents a refractive index at a wavelength of 486.1 nm, nF represents a refractive index at a wavelength of 656.3 nm, and ng represents a refractive index at a wavelength of 435.8 nm)
Meanwhile, optical materials (glass materials, organic resins, and the like) having excellent optical characteristics (high θg,F characteristic) out of the above-described certain range have also been proposed on the basis of detailed by design of the configuration (material species and molecular structure) of the optical materials. For example, polyvinyl carbazole, which is shown by A in FIG. 1 and which is an organic resin, has a secondary dispersion characteristic (high θg,F characteristic) higher than that of common organic resin materials.
In general, in a dioptric system, it is possible to reduce chromatic aberration by combining glass materials having different dispersion characteristics appropriately. For example, regarding an objective lens of a telescope or the like, chromatic aberration, which appears on an axis, is corrected by using a glass material having small dispersion and serving as a positive lens element and a glass material having large dispersion and serving as a negative lens element in combination. However, for example, in the case where the configuration and the number of lenses are limited and in the case where glass material used are limited, it may become very difficult to correct the chromatic aberration sufficiently. As for one method to solve such a problem, there is a method by making full use of a glass material having an anomalous dispersion characteristic. Optical elements have been designed by using this method.
In the case where an optical element having an excellent chromatic aberration correction function and having the shape of an aspherical surface or the like is produced, for example, molding of an organic resin on spherical glass or the like has an advantage that the mass-productivity, the moldability, the flexibility in shape, and the light-weight property are excellent as compared with use of the glass material as the material. However, the optical characteristics of the organic resin in the related art fall within a certain limited range (the secondary dispersion characteristic (θg,F) is 0.700 or less) as shown in FIG. 1, and organic resins exhibiting peculiar dispersion characteristics are very few.
Against the above-described background, in Japanese Patent Laid-Open No. 2008-158361, an optical resin composition produced by mixing N-acryloylcarbazole, a polyfunctional polyester acrylate, dimethylol tricyclodecane diacrylate, and a polymerization initiator at a predetermined ratio has been proposed. Furthermore, Japanese Patent Laid-Open No. 2008-158361 has reported that the above-described optical resin composition is worked easily and a cured product serves as a material having sufficient anomalous dispersion and durability.
However, a material having characteristics (high θg,F characteristic) within the area indicated by B in FIG. 1 and practicality (low colorability, high transparency) is not present now. Moreover, every material proposed in Japanese Patent Laid-Open No. 2008-158361 has a θg,F value of 0.70 or less.